Electrically heatable hair curler



Jan. 6, 1970- n. GsTALDER 34,438,471

` ELECTRIGALLY HETABLE 'HAIR CURLER Filed June 24.- 1968 f 5./ :fp/gi@ a n a E E n IM ven-rc2;

Aaeuf United States Patent O 3,488,471 ELECTRICALLY HEATABLE HAIR CURLER Robert Gstalder, Le Minerve Avenue Crovetto, Monaco Filed June 24, 1968, Ser. No. 739,236 Claims priority, application Monaco, June 23, 1967, 702; May 16, 1968, 54 Int. Cl. A45d 1/04; H05b 1/00, 3/42 U.S. Cl. 219--222 7 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an electrically heatable hair curler or curling roller, whose temperature may be thermostatically controlled, and more particularly to that type of feminine hair dressing accessory known as a curler whose operation is based on a difference in the expansion coefficients existing between the material of an interior core heated by an electric resistance element and that of a movable shaft mounted within the core.

The hair curler o-f this invention is totally independent of any wiring or other apparatus, except for an electric plug to which it may be attached without requiring constant supervision, overheating being automatically prevented by a thermostatic control system or device which disconnects the electric heating coil from its electric current supply circuit when the desired temperature of the curler has been attained.

Heatable hair curlers of this type comprise a tubular sheath which constitutes the curling roller and a core heated lby an electric resistance element, ywhich core is mounted in the axial bore of the sheath. The thermostatic control device is incorporated in the core. The core includes a hollow cylindrical member of an insulating plastic material over the `major part of whose length is wound a metallic wire forming a heating coil. An insulating support base held in one end of the bore of the cylindrical core member carries a metallic shaft extending axially into this bore. One of the ends of the heating coil and metallic shaft are connected to the terminals of an electric plug for supplying electric current thereto while their opposite ends are in electric contact with a folded-over, flexible metal strip arranged diametrically transversely of the core member. This strip serves as a thermostatic control when the maximum temperature desired for the hair curler has been attained.

When the heating coil is in circuit with the electric supply line and increasingly heats the plastic core member, the core member expands more rapidly than the metallic shaft. As the expansion elon gates the core member axially, it moves the shaft fixed to one of its ends with it. At a given moment in the shaft movement, its point moves out of contact with the metal strip, thus interrupting the circuit supplying the heating c-oil with electric current, and thus ending the heating of the curler.

In the operation of such hair curlers with folded-over thermostatic control strips, it has ben found that the interruption of the contact between the shaft point and the strip comes very slowly, often producing an electric arc which eventually may create a starting connection between the strip and the shaft. At this point, the thermocei static device loses its effectiveness and no longer stops the heating of the curler at the desired temperature.

In accordance with the invention, this disadvantage has been obviated by the use of a thermostatic device which causes a sudden rupture of the circuit between the metallic shaft and the heating coil at one of their ends. This thermostatic device includes a flexible metallic strip of the type of spring steel or the like into which are cut two blade portions on either side of a central axial hole. The peripheral part of the strip around the two like blade portions constitutes a stiifening frame for the strip, and the diameter of the axial hole is slightly smaller than that of a constricted portion of a groove at one end of the central metallic shaft adjacent the point of the shaft. In this manner, when the strip is mounted diametrically transversely of the shaft and core member, with the blade portion ends of the strip engaging the groove in the shaft, the blade portions will be flexed either concavely or convexly out of the plane of the stiffening frame of the strip because the larger diameter of the constricted portion of the groove will force the blade portions out of the plane of the stiffening frame and to be flexed or pivoted to one or the other side of this plane.

According ot one feature of the present invention, the metallic shaft strip whose two blade portions pivotally engage the metallic shaft groove is arranged in a transverse opening in the heated plastic core member. This transverse opening is at the end opposite to the electric current supply terminals for the shaft and the heating coil, i.e. at the head of the core member, and provides sufficient clearance for the exing of the strip between its concave-and convex end positions.

According to another feature of this invention, a male plug with two contact pins is provided for supplying electric current to the hair curler when the latter is attached thereto. The plug is detachable from the curler and its terminals are protected by a surrounding collar fixed to,V

or integral with, the socket of the plug. The collar has flattened upper portions conforming to flat wall portions in a recess of the curler sheath, which conforming portions produce a friction fit and force each plug terminal to be in contact and exact superposition with a corresponding spring contact of the electric supply circuit for the heating coil of the hair curler.

BRIEF DESCRIPTION OF DRAWING The above and other objects, advantages and feature of the present invention will become more apparent from the following detailed description of a preferred embodiment of a heatable hair curler yaccording to this invention, taken in conjunction with the raccompanying drawing wherein FIG. 1 is a side View of a heatable hair curler carrying a detachable male plug, showing the exterior of the curler;

FIG. 2 is a longitudinal section of the curler of FIG. 1 along its axis;

FIGS. 3a, 3b and 3c show the thermostatic device of the invention, on an enlarged scale, in three stages of the deformation of its flexible contact strip between the positions of being in and out of contact with the heating circuit;

FIG. 4 is a bottom view of the flexible contact strip, taken along line C-C of FIG. 3b;

FIG. 5 is a horizontal section along line A-A of FIG. 2; and

FIG. 6 is a horizontal section along line B-B of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring first to FIGS. 1, 2 and 5, the heatable hair curler or curling roller of the present invention is shown to comprise -a hollow cylinder 1 of a suitable plastic material, such as high temperature nylon. The cylinder is formed with ribs or gills 2 for holding the hair in place thereon. The cylinder 1 forms the sheath or outer envelope of the curler, and a hollow cylindrical core 3, also of a plastic material, which may be the same as that of sheath 1, is inserted in the axial bore 11 of the cylinder 1 and held therein by a friction fit. One end 4 of the core projects beyond the sheath and forms the head of the curler which takes up the hair while its other end defines a recess 5 extending transversely of the longitudinal bore 6 of the core and holding the support base 7 of central shaft 8 by a force fit. The shaft may be brass.

The core 3 has a peripheral portion of smaller diameter than that of the longitudinal bore in sheath 1 and of slightly shorter length so as to define an annular cavity 9 between the sheath and core, and the two shoulders of the core which form a friction fit with the sheath. An electric resistance 10 is wound about the core in this annular cavity out of contact with the wall of the bore 11 of the sheath.

Adjacent the projecting head 4 of core 3 and inwardly of, but adjacent, the corresponding end of the sheath 1, the core defines a diametrically extending opening 12 forming a housing for transversely arranged flexible strip 13 of a thermostatic device designed for rapid circuit interruption. The strip 13 may be of chrysocale carrying a silver contact. As best shown in FIGS. 3a, 3b, 3c, the strip has a central orifice 26 engaging an annular groove 14 at an end of central shaft 8 remote from its support base 7 and below its point 16, and the housing 12 permits the strip to be flexed into its extreme concave and convex positions shown in FIGS. 3a and 3c, respectively. The central shaft 8 has a screw-threaded end 15 which is mounted for longitudinal adjustment in a screw-threaded axial bore of base support 7 so that the shaft may be longitudinally pre-set for the desired curler temperature. The base support carries two spring contacts 17, 18 one of whose ends are mounted for contact with respective terminals 19, 20 of bi-phase electric plug 21 held by a friction fit in recess 5 of core 3. The spring contact 18 has its other end in contact with the central shaft 8 while the other end of spring contact 17 is connected to heating coil end 21. The other end 23 of heating coil 10 is connected to a contact 23 which is fixedly mounted at the base of opening 12 and engaged by one side of the flexible strip 13 when the curler is assembled (see FIG. 3a). Thus, the electric supply circuit for the heating coil 10 is constituted by the following elements: a leaf spring 17, the electric resistance wire forming the coil 10, a fixed contact 23, a flexible strip 13, the metallic central shaft 8, and the other leaf spring 18.

The operation of the thermostatic device of this invention will now be described with particular reference to FIGS. 3a, 3b, 3c and 4. This device is constituted by a flexible metallic strip of the type of spring steel or the like, somewhat like a razor blade, which has two like blade portions 24, 25 cut into it at respective sides of central hole 26. The peripheral part of the strip 13 around the two blade portions constitutes a stiffening frame for the strip, and the diameter of hole 26 of the strip is slightly smaller than that of the constricted portion of the groove 14 in central shaft 8. Thus, when the strip is mounted on the shaft, its blades 24 and 2S take on a convex (FIG. 3a) or concave (FIG. 3c) shape because they cannot remain in the plane of the sfiffening frame due t0 the flexing power of these blades engaging the constricted portion of groove 14.

The operation of this thermostatic device is obvious from the drawing. When the curler is mounted on plug 21, the two spring contacts 17, 18 engage the terminals 19, 20, thus causing the electrical resistance wire 10 to be in circuit and to be supplied with electric current to heat the core 3 and simultaneously the sheath 1 of the curler while the central shaft 8 receives only heat radiated through the wall of core 3, i.e. very little.

Considering that the coefficient of expansion of the plastic material constituting the core 3 and the cylindrical sheath 1 is greater than that of metallic shaft 8, the shaft will be progressively moved longitudinally by the elongation of the core to which it is attached, as the heating of the core causes such elongation. This will push the strip 13 from its convex position shown in FIG. 3a to a more or less planar position perpendicular to shaft 8, as shown in FIG. 3b. As previously pointed out, the strip can remain engaged with the shaft only in a concave or convex position of its blades. Therefore, the continued elongation of the core 3 will at one point suddenly force the strip into its concave position shown in FIG. 3c, causing the sudden interruption of the electric supply circuit for the heating coil 10, the spring having been moved away from contact 23. At this point, the curling roller is at the desired temperature for use.

As the curler cools off, the core and sheath progressively return to their original lengths, i.e. their lengths at ambient temperature, the strip is returned to its convex position and the circuit is suddenly closed in the same manner as it was suddenly opened.

The special plug devised for use with the curler according to the invention will now be described with reference to FIGS. 2 and 6.

The plug comprises a cylindrical socket 26 having an axially extending projecting portion 27 insulating the terminals 19 and 20 from each other. The terminals are connected to contact pins 19', 20 of the plug. The socket and projecting portion of the plug are molded in one piece about the electrically conductive terminals and contact pins of a suitable insulating material, A flanged collar 28 is fixed to the socket 26 and extends axially slightly below the socket portion 27 but above the ends of terminals 19, 2f). Thus, there is no danger of electrocution when the curler is removed from male plug 21 while the same remains attached to a corresponding female outlet. It will be noted that the cylindrical collar 28 has flattened upper portions 29, 30 for frictional engagement with recess 5 of the curler core 3, which has conforming flat wall portions to assure that the spring contacts 17 and 18 come into proper contact with terminals 19, 20 of the plug when the curler is mounted thereon.

The present invention is not limited to the illustrated embodiment and many variations and modifications will occur to those skilled in the art without departing from the spirit and scope thereof.

I claim:

1. An electrically heatable hair curler, comprising (l) an outer sheath of plastic material having an inner wall defining a longitudinal bore,

(2) a hollow cylindrical core of plastic material having an outer wall and defining a longitudinal bore,

(a) the outer wall of the core having two shoulders forming a friction fit with the inner wall of the outer sheath, and

(b) the outer wall of the core having a peripheral `iportion of smaller diameter than that of the longitudinal bore of the outer sheath and of slightly shorter length than the latter bore, the peripheral portion of the outer wall of the core and the inner wall of the sheath defining an annular cavity therebetween,

(c) one of the ends of the core defining a recess extending transversely of the longitudinal bore of the core, and

(d) the other end of the core defining a diametrically extending opening,

(3) a conductive central shaft extending in the longitudinal bore of the cylindrical core from said one to the other end thereof,

(4) a support base for the central shaft mounted in the recess in the one end of the care,

(e) one of the ends of the central shaft being mounted on the support base for longitudinal adjustment therein,

(5) an electric resistance wire helically wound about the outer wall of the core out of contact with the inner wall of the sheath, said wire forming a heating coil in said annular cavity having one end adjacent the one end of the core and another end adjacent the other core end,

(6) a metallic strip having two flexible blades extendin transversely of the central shaft and housed in said diametrically extending opening in the core,

(f) one of the blades being arranged for contact with the one heating coil end and the other blade being in pivotal contact with the other shaft end, v

(7) two spring contacts mounted in the support base and each contact having two ends,

(8) a male electric plug mounted in the recess in the one end of the core,

(g) the plug having two terminals,

(h) the one ends of the spring contacts being arranged for contact with the terminals, and

(i) the other ends of the spring contacts being in respective contact with the one heating coil end and with the central shaft,

(j) an electric current supply circuit being constituted by said terminals, spring contacts, heating coil, metallic strip and central shaft for heating the coil when the curler is mounted on the plug and the plug is connected to a source of electric current, and

(9) the plastic material of the core having a larger coefficient of heat expansion than the metal of the central shaft whereby, upon heating of the core by the heating coil, the plastic core will progressively expand more rapidly than the central shaft, thus moving the shaft longitudinally and taking along the metallic strip which is in pivotal contact therewith until the one blade is out of contact with the one heating coil end and the electric current supply circuit is interrupted to discontinue heating.

2. The hair curler of claim 1, further comprising a plurality of gills on the outer sheath for holding hair in place thereon.

3. The hair curler of claim 1, further comprising anv end of the core projecting outwardly of the sheath beyond the one core end and forming the head of the curler for taking up the hair.

4. The hair curler of claim 1, wherein the support base is mounted in the recess with a force fit.

5. The hair curler of claim l, wherein the one shaft end is screw-threadedly mounted in a screw-threaded axial bore of the support base.

6. The hair curler of claim 1, wherein the metallic strip has two like blade portions cut thereinto at respective sides of a central hole, a peripheral part of the strip around the two blade portions constituting a stiffening frame for the strip, the other shaft end defines a groove having a constricted portion, the diameter of the central hole being slightly smaller than that of the constricted groove portion and the blade portions pivotally engaging the constricted groove portion of the shaft with the central hole, the flexible blade portions being thus forced out of the plane of the stiffening frame of the strip into a convex or concave end position, and the diametrically extending opening in the core permitting the displacement of the strip with the longitudinal movement of the shaft, a contact in connection with the one heating coil end mounted in said opening and ya mating contact on the metallic strip, said contacts being in circuit in the convex end position and out of circuit in the concave end position.

7. The hair curler of claim 1, wherein the male electric plug is detachably mounted in the recess and comprises a cylindrical socket having an axially extending projecting portion insulating the terminals from each other, and a anged collar xed to the socket and extending axially slightly below the socket portion but above the ends of the terminals, the collar having a pair of attened upper portions for frictional engagement with conforming flat wall portions of the recess in the core.

References Cited UNITED STATES PATENTS 1,884,232 10/1932 Rehm 219-225 2,475,376 7/1949 Darling 219--241 FOREIGN PATENTS 651,924 4/ 1951 Great Britain. 663.214 12/1951 Great Britain.

ANTHONY BARTIS, Primary Examiner U.S. Cl. X.R. 

